The Ultimate Guide To Amino Acid Supplements

Amino Acid Supplements

If you’ve ever been to the gym, you’ve probably seen them.  Those pretty, bright-colored liquids in water bottles, shakers, or gallon jugs being carried along and sipped on every now and then.  Those are amino acid supplements…

In recent years, amino acids have gone from one of the most obscure kinds of supplements to one of the most sought after.  Everyone, from traditional bodybuilders to crossfitters to yoga moms, is down with amino acid supplements…

But do they actually work?  Are they worth your hard earned money?  Is this just another way for supplement companies to make money?

Well, we’ll be sure to answer all that and more throughout this article, but first, let’s make sure we have a basic understanding of what exactly amino acids are.  Then we’ll discuss how important they are as supplements…

What Are Amino Acids?

Put simply, Amino Acids are the building-blocks of proteins.  Proteins are required by the body to form structures (like muscle and organ tissue) and carry out various processes.  All proteins are just different compositions of Amino Acids.

Amino Acids themselves are made up of different arrangements of elements.

Amino Acids are considered organic molecules because they contain at least one atom of the element, Carbon.  Carbon is unique in that each atom is capable of creating up to 4 bonds with other elements.  This is what has allowed molecules to become more and more complex over time, eventually (though we still don’t now exactly how) resulting in life.

Without Carbon, elements would just pass each other by and nothing more complex would ever exist.  So really, we should all be thanking Carbon for allowing complex organic molecules to exist, especially Amino Acids…

Different Types Of Amino Acids

Amino Acids have various distinctions which allow them to be grouped together and classified in certain ways.  Perhaps the most important distinction pertaining to Amino Acids is the difference between Proteinogenic Amino Acids and Non-Proteinogenic Amino Acids.

Proteinogenic Amino Acids Vs Non-Proteinogenic Amino Acids

The first distinction that’s usually made between amino acids is whether they are proteinogenic or non-proteinogenic.

Proteinogenic Amino Acids, as the name implies, are Amino Acids that the body can use to construct the complete proteins that form our genetic code.  There are 20 of these.

  1. Alanine
  2. Arginine
  3. Asparagine
  4. Aspartic acid
  5. Cysteine
  6. Glutamic acid
  7. Glutamine
  8. Glycine
  9. Histidine
  10. Isoleucine
  11. Leucine
  12. Lysine
  13. Methionine
  14. Phenylalanine
  15. Proline
  16. Serine
  17. Threonine
  18. Tryptophan
  19. Tyrosine
  20. Valine

It’s important to understand that when we talk about Proteinogenic amino acids, we’re not just talking about muscle.  We’re talking about ALL proteins.

Non-Proteinogenic Amino Acids are simply Amino Acids that are not used to make proteins.  There are hundreds of these found naturally.

Although these types of Amino Acids are not used to create proteins, many of them may possess important biological functions such as acting as an intermediate in the biosynthesis of neurotransmitters.

Some of the most common Non-proteinogenic Amino Acids used as supplements are:

Obviously, with over a hundred of these little guys in existence, we could go on for hours.  The important thing is to understand that:

  1. Not all Amino Acids are used to make proteins
  2. Non-proteinogenic Amino Acids can be just as important

So Nonproteinogenic Amino Acids can (and are) of vital importance, and there are hundreds of them found throughout the human body and nature.

However, when we talk about Amino Acids in the context of nutrition, we usually talk about the Proteinogenic Amino Acids.

Grouping Of Proteinogenic Amino Acids

Most of the time, when we’re talking about Amino Acids in the context of nutrition, training, whatever, we’re talking about Proteinogenic Amino Acids.  This type of Amino Acid can be further broken down into different groups, based on dietary need and physiological ability to produce it.

  1. Essential
  2. Nonessential
  3. Conditionally Essential

Before we get to talking about each individual Amino Acid, we need to  first understand what makes them either essential, nonessential, or conditionally essential.

Essential Amino Acids

Essential Amino Acids (EAAs) are the Amino Acids which the human body is not capable of producing.  They must be obtained through diet (or supplementation).

There are 9 Essential Amino Acids:

  1. Histidine
  2. Isoleucine
  3. Leucine
  4. Lysine
  5. Methionine
  6. Phenylalanine
  7. Threonine
  8. Tryptophan
  9. Valine

Nonessential Amino Acids

Nonessential Amino Acids are Amino Acids which the human body is capable of producing on it’s own.  This usually happens through the conversion or combination of Essential Amino Acids

  1. Alanine
  2. Arginine
  3. Asparagine
  4. Aspartic acid
  5. Cysteine
  6. Glutamic acid
  7. Glutamine
  8. Glycine
  9. Proline
  10. Serine
  11. Tyrosine

Conditionally Essential Amino Acids

Conditionally Essential Amino Acids are Amino Acids that can usually be produced by the human body, except under certain circumstances such as stress or diet-related issues.

In other words, under certain conditions, they become essential.

There are 6 of these:

  1. Arginine
  2. Cysteine
  3. Glutamine
  4. Tyrosine
  5. Glycine
  6. Proline

When everything is functioning as it should be, you don’t need to worry about getting enough of these Amino Acids.  However, in certain circumstances, the body may become incapable of producing these and, in that case, they become essential.

A Closer Look At The 20 Amino Acids That Make Up Our Genetic Code

There are 20 unique proteinogenic amino acids.

  1. Alanine
  2. Arginine
  3. Asparagine
  4. Aspartic acid
  5. Cysteine
  6. Glutamic acid
  7. Glutamine
  8. Glycine
  9. Histidine
  10. Isoleucine
  11. Leucine
  12. Lysine
  13. Methionine
  14. Phenylalanine
  15. Proline
  16. Serine
  17. Threonine
  18. Tryptophan
  19. Tyrosine
  20. Valine

Here’s a quick run-down on each one…



L-Alanine is a nonessential amino acid which is involved in  a variety of bodily functions.

What Roles Does Alanine Play In The Body?

Alanine plays a vital role in Glucose metabolism.

It is a key component in the glucose–alanine cycle, which is a process by which Pyruvate and Glutamate is transported from the muscle tissue to the liver and Glucose is returned.  It takes place in the liver in order to spare muscle tissue the process of gluconeogenesis, leaving more ATP available for muscle contractions.

Where Does L-Alanine Come From?

Since Alanine is a nonessential amino acid, the body is capable of synthesizing it on it’s own.  It generally does this by converting Pyruvate through a chemical process known as reductive amination.

As it turns out, Branched Chain Amino Acids (BCAAs) — Leucine, Isoleucine, and Valine — contribute a large chunk of the Nitrogen needed for Alanine production, so adequate BCAA consumption (either through diet or supplementation) is an important condition that needs to be met for your body to produce Alanine.

Although your body can technically produce Alanine, and does to some extent, you can easily get it from your diet.

Foods that contain a good amount of Alanine include:

  • Meat (seafood included)
  • Nuts
  • Whole Grains

So it’s actually tough to envision a situation in which you wouldn’t be getting adequate Alanine from your diet anyway.  Even vegetarians and vegans get plenty of Alanine most of the time.

Are There Any Benefits To Taking L-Alanine Supplements?

Not really.  Given the fact that your body can make it’s own Alanine fairly easily AND it’s VERY available in the average diet, there’s no reason to supplement with L-Alanine.  Still, supplement companies love to toss L-Alanine in their amino acid supplements.


Because it’s cheap, virtually tasteless (does impact flavor if it’s a powder supplement), and they can back it up with BS, ambiguous claims like “it’s vital for glucose metabolism”.  Just because something is essential for your health doesn’t mean you need to supplement with it and L-Alanine is one of  those things.

Key Takeaways For L-Alanine

Alanine is an important amino acid for the proper functioning of our bodies, but supplementation is pretty much useless.  Even if you eat a low-protein diet which doesn’t yield enough L-Alanine, your body can make it by itself.

Alanine is often used in amino acid supplements as a random ingredient, but there’s no point.  No matter what a supplement company tells you, there’s just no real reason to use L-Alanine supplements (except in some very rare instances).



Arginine is a conditionally essential amino acid which the body can manufacturer by converting the amino acid Citrulline.  It is used to build muscle protein but has a ton of other biologically important functions as well.

What Role Does Arginine play in the body?

Arginine serves as a substrate or intermediate in the production of several important substances in the body, including (but not limited to):

  • Nitric Oxide
  • Creatine
  • Urea

Naturally, L-Arginine supplements have been sold with claims like “Arginine increases blood flow” and “Arginine enhances performance”, but in reality, it doesn’t.

Where Does Arginine Come From?

Arginine is ordinarily considered a nonessential amino acid because the body can fairly easily make it by converting the amino acid Citrulline.  However, it’s considered conditionally essential because, in certain instances, the body may be unable to make it.

For example, pre-term infants are unable to synthesize Arginine internally, so they need to obtain it nutritionally.

Foods that contain a lot of L-Arginine include:

  • Meat
  • Seeds/Nuts
  • Dairy
  • Spirulina

As with Alanine, it’s difficult to envision a scenario where your diet wouldn’t provide enough Arginine, but it can happen if you eat an abnormally low protein diet.

Good thing your body can just make Arginine from Citrulline!

Are There Any Benefits To Taking L-Arginine Supplements?

Arginine pretty much sucks as a supplement.  Studies show it may help enhance blood flow in people with compromised blood flow, but it has failed to increase blood flow or impact exercise performance in healthy people.

If you want the benefits of L-Arginine, you should really be supplementing with L-Citrulline, not Arginine.  Sure, it’s the pre-cursor to Arginine but it’s actually much more effective as a supplement.

Key Takeaways For L-Arginine

Arginine is without a doubt one of the most versatile amino acids the human body needs to function properly.  It’s not only involved in protein synthesis.  It plays several important roles throughout the body.

Although Arginine supplements are usually marketed as performance enhancers and pump enhancers, it’s not a very effective supplement at all.  L-Citrulline is actually much more effective at basically all of the things L-Arginine is supposed to do.



Asparagine is an amino acid which, as the name implies, is found in Asparagus.

What Roles Does Asparagine Plat In The Body?

Asparagine is mostly used for constructing proteins.  It doens’t have as many other functions as Arginine for example, but is required for healthy brain function and ammonia production.

Where Does Asparagine Come From?

Asparagine can be synthesized by the body from Oxaloacetic Acid.

Foods with high amounts of Asparagine include:

  • Meat
  • Dairy
  • Asparagus
  • Whole Grains
  • Potatoes

Unless you eat a low-protein, poor-quality carb diet, you’re unlikely to not get enough Asparagine.

Are There Any Benefits To Taking Asparagine Supplements?

If there’s an ingredient that’s legal to sell as a supplement, there will always be a someone selling it as a supplement…Asparagine is no exception.

There’s no real reason to take Asparagine supplements though.  That is, unless you somehow don’t eat foods with Asparagine (unlikely) and have a problem with your Oxaloacetic Acid levels.

Asparagine supplementation has been shown to encourage better glucose metablism and improve some aspects of exercise in mice when combined with Aspartic Acid, but no human studies have confirmed these findings.

Key Takeaways For Asparagine

Asparagine isn’t necessarily as “important” as amino acids like Arginine, but like any amino acid, you need it.  If you aren’t getting enough through your diet, your body will synthesize it though, so there’s not much to worry about there.

Asparagine supplementation is probably pretty useless, although some modest benefits have been noted in rodent studies.

Aspartic Acid

Aspartic Acid

Aspartic Acid, also known as Aspartate, is a nonessential amino acid which is actually pretty similar to Asparagine in a lot of ways.  It was first discovered through hydrolysis of Asparagine, actually.

What Roles Does Aspartic Acid Play In The Body?

In addition to being used to construct muscle proteins, Aspartic Acid is involved in the Urea cycle.  This is the cycle through which Ammonia, a toxic byproduct, is converted into a less harmful substance — Urea — which is then excreted from the body.

Aspartic Acid doesn’t play as a big a role as amino acids like Arginine or Citrulline, but it is important nonetheless.

Aspartic Acid donates an amino group to combined with Ammonia and form Urea.  Without it, this process could not take place.

Where Does It Come From?

Just like Asparagine, Aspartic Acid can be synthesized by the body from Oxaloacetic Acid.

In terms of food sources, it can be found in:

  • Meat
  • Dairy
  • Cabbage
  • Asparagus
  • Egg Whites

So, it’s pretty unlikely that you’re not getting enough Aspartic Acid.  And, even if you are, your body can easily make it.

Are There Any Benefits To Taking Aspartic Acid Supplements?

Like Asparagine, L-Aspartic Acid is pretty useless as a supplement.  Some studies in rodents indicate it may help with exercise fatigue, but these findings have not been replicated in human studies.

D-Aspartic Acid, but which is the D-form of Aspartic Acid, has been investigated for Testosterone-boosting effects.  It’s not clear how useful it really is or building muscle though, since you need a much larger increase in Testosterone to accelerate muscle growth.

Key Takeaways For Aspartic Acid

Aspartic Acid is a nonessential amino acid, so your body can make it if you don’t get enough from your diet.  The only way that would happen though is if you eat a low-protein, few-vegetable diet…and they just happen to be vegetables that don’t contain Aspartic Acid.

In other words, Aspartic Acid deficiency is unlikely.

Supplementation is pretty useless, but D-Aspartic Acid is used as a test-booster.



Cysteine is a unique sulfur-containing amino acid which does a lot more than just help form complete proteins.

What Roles Does Cysteine Play In The Body?

Cysteine is proteinogenic, but it’s also required for Glutathione synthesis.  Glutathione is what we call the body’s “master anti-oxidant”.

It’s produced in the liver and it’s function is pretty simple: Detoxification.  So Cysteine is essential  for the body to properly detoxify and minimize oxidative damage caused by free radicals.

By binding with heavy metal ions, Cysteine also helps rid the body of excess heavy metals like Cadmium, Lead, and Mercury.

Where Does It Come From?

In the body, Cysteine is manufactured through a combination of the amino acids Serine and Methionine.  Serine provides most of the structure, but Methionine provides the sulfur group.

Given that the sulfur group is what gives Cysteine most of the distinct roles it plays, it would be an over-simplification to say that Cysteine is simply “Serine with a sulfur group attached”.

You can always get your Cysteine from consuming high protein foods like:

  • Meat
  • Eggs
  • Fish
  • Nuts/Seeds
  • Beans/Oats/Whole Grains

If you’re a vegetarian, vegan, or otherwise consume a low-protein diet, you may not be getting enough Cysteine.  If that’s the case, your body is probably producing it from all the available Serine and Methionine.

Are There Any Benefits To Taking Cysteine Supplements?

Cysteine supplements are usually found in the form N-Acetyl-Cysteine (NAC).  This form is more bioavailable than L-Cysteine and has been the preferred form in the majority of clinical trials involving Cysteine and toxicity.

NAC supplementation has been shown to:

So yeah, in certain circumstances, Cysteine (usually as NAC) can be a very useful supplement.

Key Takeaways For Cysteine

Cysteine is important, not only for bulding muscle, but also as a detoxifying agent throughout the body.  It’s most distinguished role is in helping to create Glutathione, the body’s most powerful anti-oxidant.

As a supplement, you’ll usually find it in the form of N-Acetyl-Cysteine (NAC), which is effective in certain situations (such as toxic over-dose).

Glutamic Acid

L-Glutamic Acid

Glutamic Acid, also known as Glutamate, is a nonessential amino acid which has plenty of significance beyond simply building proteins.

What Roles Does Glutamic Acid Play In The Body?

Glutamic Acid is used to form whole proteins, but that’s not why it’s so important.  It also functions as a neurotransmitter.  In fact, Glutamic Acid the most prevalent excitatory neurotransmitter in our nervous systems.

This makes it incredibly important for pretty much anything related to cognitive function, including learning and memory.

Glutamic Acid is also needed for the synthesis of the chief inhibitory neurotransmitter, GABA.

Where Does It Come From?

The body is capable of making Glutamic Acid through a series of processes involving Glucose, Pyruvate, and Oxaloacetate.  It can also be found in many high-protein foods such as:

  • Shellfish
  • Meat
  • Soy

You may have also heard of the sodium salt version of Glutamic Acid, Monosodium Glutamate, or MSG.  It’s used throughout the world as a food additive to enhance flavor.

This has in turn boosted the demand for Glutamic Acid and made it the most widely produced amino acid in the world.

Are There Any Benefits To Taking Glutamic Acid Supplements?

Like most of the nonessential amino acids we’ve discussed, supplementing with Glutamic Acid is usually pointless.  You probably get plenty of it through your diet and, even if you don’t, your body can just make it.

You’ll occasionally see Glutamic Acid present in amino acid supplements, but it’s one of the least important amino acids you could possibly include in those types of products.

Key Takeaways For Glutamic Acid

Glutamic Acid is extremely important within the body.  It’s one of the few proteinogenic amino acid that isn’t a precursor to a neurotransmitter, but is an actual neurotransmitter.

As the chief excitatory neurotransmitter in the brain, and a substrate for the chief inhibitory neurotransmitter, Glutamic Acid is vastly important for central nervous system and cognitive function.

Supplementation with Glutamic Acid is pretty much useless though.



Glutamine is a nonessential amino acid which becomes essential under certain circumstances, making it a conditionally essential amino acid.

What Roles Does Glutamine Play In The Body?

Like the other 19 amino acids discussed in this section, Glutamine is used to form complete proteins, but it also has other roles throughout the body.

It’s required for proper:

  • Immune function
  • Digestive health
  • Glutathione synthesis

So yeah, Glutamine is one of those amino acids that serves multiple purposes.

Where Does It Come From?

Glutamine can be produced by our bodies (assuming were healthy) from Glutamic Acid and Ammonia.  It can also be found in tons of foods including:

  • Meat
  • Dairy
  • Beans
  • Cabbage
  • Asparagus

Due to illness or injury, it’s possible that Glutamine transitions from a nonessential to an essential amino acid.  For this reason, Glutamine supplements are extremely popular.  Are they worth it though?

Are There Any Benefits To Taking Glutamine Supplements?

Glutamine is one of the most widely used amino acid supplements.  It is frequently grouped together with Leucine, Isoleucine, and Valine in the form of BCAA supplements.

The claims made about Glutamine supplements basically mirror its biological significance.  Glutamine supplements supposedly:

  • build muscle
  • enhance performance
  • boost immunity

Unfortunately, research has proven that, while Glutamine itself is extremely important in the body, supplementation is ineffective for building muscle or enhancing performance.

There’s also not much evidence that it helps with immune boosting, but it may be useful during long-duration exercise when Glutamine levels get depleted and exercise-induced immune suppression can occur.

Other than that, Glutamine supplements are pretty useless.

Key Takeaways For Aspartic Acid

Glutamine is an extremely important conditionally essential amino acid.  It’s required for a wide variety of bodily functions, but Glutamine supplements are a massive disappointment.

Out of all the amino acid supplements, Glutamine is perhaps the most overrated.



As you can probably tell from the picture above, Glycine is the simplest of all the amino acids in terms of its chemical structure.  It’s considered nonessential or possibly conditionally essential.

What Roles Does Glycine Play In The Body?

Glycine is used to make proteins, but is also a major inhibitory neurotransmitter in the Central Nervous System (CNS).  Glycine can be synthesized by the body from the amino acid Serine.

Most of the Glycine produced by the body is used for neurotransmitter purposes, but some of it is used to produce Collagen as well.

This role means that Glycine can impact various aspects of cognitive function including:

  • Memory
  • Learning
  • Sleep

We’ll discuss how Glycine supplementation may impact these things a little later on…

Where Does It Come From?

The body can synthesize Glycine from the amino acid Serine and this process is dependent on Folic Acid (Vitamin B9).  In terms of foods, Glycine is pretty widespread.

Pretty much anything that’s high in protein will contain a decent amount of Glycine.  Some of the higher Glycine foods are:

  • Meat
  • Fish
  • Shellfish
  • Seaweed

Assuming you get plenty of Serine in your diet already, you don’t need to worry about Glycine, but if you need it, it’s pretty easy to get via your diet.

Are There Any Benefits To Taking Glycine Supplements?

Glycine is often incorporated into amino acid supplements because it’s cheap and tastes sweet (like sugar almost).  Unfortunately, most of the reasons provided by supplement companies for why you should supplement with Glycine are based on nothing.

Glycine definitely has an important function in the brain and Central Nervous System, but the only proven benefit of supplementation is with regards to sleep.

Glycine supplementation has been shown to improve quality of sleep in multiple studies, though it’s still not clear how exactly.  The clinically effective dose is 3 grams prior to bed.

Key Takeaways For Glycine

Glycine is the simplest of all amino acids.  It’s important for certain brain and bodily functions, but supplementation has only been shown to enhance sleep quality.

As far as amino acid supplements, Glycine is definitely not the most useful, but it does have it’s purpose.



Histidine is an essential amino acid, meaning the body cannot produce it and it must be instead obtained via diet.

What Roles Does Histidine Play In The Body?

In addition to being used to form whole proteins, Histidine is also the precursor to Histamine, an important chemical involved with our immune response.

It’s also one of the pre-cursors involved in Carnosine synthesis, the other being Beta-Alanine.  However, Histidine is not considered particularly important for Carnosine synthesis since Beta-Alanine is the rate-limiting factor.

Where Does It Come From?

As mentioned above, the body can’t make Histidine from scratch like it can with other (nonessential) amino acids.  Instead, you need to obtain all your Histidine from the foods you eat.

Naturally, Histidine is present in any complete protein food such as:

  • Meat
  • Dairy
  • Eggs

But can also be found in:

  • Beans
  • Rice
  • Bananas

The only people who need to go out of their way to ensure adequate Histidine consumption are Vegans and Vegetarians.  If you eat complete protein-rich foods like Meat and Fish, you’re good.

Are There Any Benefits To Taking Histidine Supplements?

Histidine is sometimes included in amino acid supplements along with Beta-Alanine because both of them are needed to produce Carnosine, a dipeptide which enhances muscular endurance.

However, because Histidine is not the rate limiting factor here, supplementation isn’t going to boost Carnosine synthesis like supplementation with Beta-Alanine will.

For that reason, although Histidine is an essential amino acid, supplementation is usually pretty useless.  Unless you’re Histidine deficient (which would likely mean you’re just protein deficient in general), you don’t need Histidine supplements.

Key Takeaways For Histidine

Histidine is an important amino acid, not just for building muscle, but also for proper immune function.  It’s the direct precursor to Histamine and is also needed for Carnosine synthesis (the target of Beta-Alanine).

Eve though Histidine is considered an essential amino acid, meaning the body cannot produce it, supplementation is pretty much pointless.



Isoleucine is one of the 3 Branched Chain Amino Acids (BCAAs), along with Leucine and Valine.

What Roles Does Isoleucine Play In The Body?

As one of the three Branched Chain Amino Acids, Isoleucine has a particularly high concentration in muscle tissue where it appears to play a role in Glucose uptake.

This is really the only distinguishing factor of Isoleucine compared to the other BCAAs, Leucine and Valine.  Other than that, there’s nothing particularly special about Isoleucine.

Where Does It Come From?

Isoleucine is an essential amino acid, meaning it cannot be made inside the body.  Instead, it must be obtained through your diet.

Complete-protein foods tend to carry high amounts of Isoleucine.  That includes the usual suspects like:

  • Any Kind Of Meat
  • Dairy
  • Fish

But plant sources of Isoleucine include:

  • Swiss Chard
  • Seaweed
  • Beans

Anything that has high levels of BCAAs, including Whey Protein and BCAA supplements, will tend to yield a decent amount of Isoleucine.

Are There Any Benefits To Taking Isoleucine Supplements?

Isoleucine is most commonly found in BCAA supplements and amino acid supplements geared toward Bodybuilding.

In truth, Isoleucine isn’t the most important BCAA in this regard.  Leucine is the clear winner in terms of building muscle, but Isoleucine appears to promote Glucose uptake into muscle tissue.

For this reason, it is often included alongside Leucine and Valine.  You won’t usually find Isoleucine by itself.

Key Takeaways For Isoleucine

Isoleucine is basically the second most important BCAA.  Not quite as important as Leucine, but more important than Valine for sure.

As a supplement, you’ll usually see Isoleucine grouped together with Leucine and Valine (BCAA supplements).  This makes sense since, by itself, it’s not particularly useful for anything.



Leucine is considered by many who hit the weights to be the “most important” amino acid.  While you can’t really compare the importance of essential amino acids though (because you need them all), it’s definitely the most important when it comes to building muscle.

What Roles Does Leucine Play In The Body?

Although all of the 20 amino acids are used, to some degree, to build muscle, Leucine is the undisputed king.

Not only does Leucine make up a larger proportion of muscle protein than all other amino acids, it also directly stimulates muscle protein synthesis.

Leucine works via activating the signaling protein, mTOR, which tells the body to start bulding muscle tissue from individual amino acids.

This is why many bodybuilders (and pretty much anyone who lifts) consider Leucine especially important.  It is when it comes to building muscle.

Where Does It Come From?

Leucine, being an essential amino acid, cannot be manufactured by the body.  You must obtain all your Leucine from food like:

  • Meat
  • Fish
  • Dairy
  • Soy
  • Beans

Most plant sources of Leucine (besides Soy and Beans) do not contain very much.

If you’re a vegetarian and you care about building muscle, you need to pay special attention to how much Leucine you’re getting.

You can get it from non-animal based foods, but you need a lot.  It’s just way easier to get Leucine from animal products.

Are There Any Benefits To Taking Leucine Supplements?

Leucine is widely used by bodybuilders, athletes, and anyone else concerned with building muscle.  But is it actually necessary?  Well, no…

If you get enough protein (1.2-1.5g/lb of bodyweight), there comes a point where Leucine will no longer help you build more muscle.

However, the fact remains that most people don’t get anywhere near enough protein to achieve their fitness goals, so Leucine may be useful in more situations than we’d like to think.

Vegetarians and Vegans are particularly likely to benefit from Leucine supplementation with regards to building muscle, since they are the most likely to be deficient.

Key Takeaways For Leucine

Leucine is the most important amino acid with regards to building muscle.   It directly stimulates muscle protein synthesis by activating the signaling molecule, mTOR.

If you don’t get enough protein, you may derive some benefit from Leucine supplementation.  If you do get enough protein, you probably won’t benefit that much.



Lysine is an essential amino acid, so you can’t make it and have to get it from food.  That said, the body is relatively good at conserving it, so deficiency is rare.

What Roles Does Lysine Play In The Body?

Aside from being used to build complete proteins, Lysine plays a role in digestive, immune, and connective tissue health.  More specifically, Lysine is one of the key components needed for the body to make Collagen and Elastin.

These two substances are vital for the health of connective tissues and joints.

Other than that, Lysine doesn’t really do much.  It’s definitely not one of those amino acids (like Arginine) that steals the spotlight.

It builds proteins, encourages connective tissue health, and supports immune function.  That’s about it…

Where Does It Come From?

Since Lysine is an essential amino acid, it can’t be manufactured within the body and must instead be obtained through diet.

As usual, you’ll find Lysine in complete protein foods like:

  • Dairy
  • Meat
  • Fish

But you can also find it in plenty of plant-based foods.  A few of the highest Lysine plant-based foods are:

  • Lentils
  • Quinoa
  • Soy

Obviously, there are a ton of foods that contain Lysine to some degree, but these are a few of the best foods to get Lysine if you don’t eat meat or animal products.

Are There Any Benefits To Taking Lysine Supplements?

The only real reason to supplement with Lysine is to help manage Herpes flair-ups.  It’s not particularly effective for anything else, but it is definitely helpful in this regard.

Key Takeaways For Lysine

Lysine is an essential amino acid that plays a role in immune, digestive, and connective tissue health.  As a supplement, it’s only useful for treating symptoms of Herpes (but not the actual Virus).

As long as you’re getting plenty of protein, you don’t need to worry about taking a Lysine supplement.  You won’t find it in many amino acid supplements.



Like Cysteine, Methionine is a sulfur-containing amino acid.  Unlike Cysteine, however, the body can’t make Methionine.  It’s an essential amino acid.

What Roles Does Methionine Play In The Body?

Methionine is the only essential amino acid which contains sulfur.  This property is what makes it so special in terms of how it contributes within the body.

It plays a vital role in various processes related to:

  • Digestive Health
  • Blood Vessel Formation
  • Detoxification

Methionine is a precursor to Cysteine and Taurine, so it makes sense that it has potent antioxidant properties.

Where Does It Come From?

Methionine can’t be made in the body and must be obtained from food.  Some foods that are particularly high in Methionine include:

  • Meat
  • Dairy
  • Sesame Seeds
  • Brazil Nuts
  • Soy

It’s unlikely that you’re deficient in Methionine unless you’re not getting enough protein.  Naturally, the most likely candidates here are Vegetarians and Vegans.

With some simple meal-planning, however, you can avoid the risk entirely.  It’s not hard to make sure you get enough Methionine.

Are There Any Benefits To Taking Methionine Supplements?

Unlike most other amino acid supplements, Methionine is useful for more than one thing…

It has been investigated as a potential treatment for Parkinson’s Disease and Urinary Tract Infections.  It has also been shown to reduce Homocysteine levels.

You won’t usually see Methionine in powder-form amino acid supplements because it tastes very bad.

Key Takeaways For Methionine

Methionine is the an essential amino acid which plays a part in a fairly diverse range of bodily functions.  Supplementation is usually not needed, but in some situations it can be quite useful.



Phenylalanine is an essential amino acid which serves as the precursor to Tyrosine.

What Roles Does Phenylalanine Play In The Body?

Like the other 19 proteinogenic amino acids, Phenylalanine is used to build muscle proteins.  However, it’s more important role has to do with the neurotransmitters in your brain.

Specifically, Dopamine and Noradrenaline.

Phenylalanine is the first step in the multi-step process of Catecholamine synthesis.  First, Phenylalanine is used to make Tyrosine.  Tyrosine is then converted into L-Dopa.  L-Dopa is converted into Dopamine and Dopamine.  Dopamine Adrenaline and Noradrenaline.

As a collective, these neurotransmitters are involved with:

  • Mood
  • Energy Levels
  • Cognitive Ability
  • Muscle Function
  • Sleep

Needless to say, Phenylalanine is a very important amino acid.  It’s believed to be the primary reason why a high protein diet is beneficial for cognitive function.

Where Does It Come From?

Naturally, Phenylalanine is found in all complete protein foods:

  • Meat
  • Fish
  • Dairy

But can also be found in the following plant-based foods as well:

  • Seaweed
  • Beans
  • Turnips
  • Spinach
  • Swiss Chard

So, if you’re a vegetarian or vegan, you want to make sure you’re getting plenty of Phenylalanine from Phenylalanine-rich foods.

Are There Any Benefits To Taking Phenylalanine Supplements?

Phenylalanine is grouped in with other essential amino acids in the form of EAA supplements, but there isn’t much research on Phenylalanine supplementation in healthy human subjects.

If you aren’t getting enough Phenylalanine through your diet, you may benefit from Phenylalanine supplementation in some way.  These benefits would be basically the same as what you get with L-Tyrosine supplementation.

Key Takeaways For Phenylalanine

Phenylalanine is an extremely important essential amino acid.  It does a lot more than just form complete proteins.  As the first step in Catecholamine synthesis, Phenylalanine fuels a wide array of mental and physical functions.

Supplementation isn’t necessary unless you’re not getting enough protein.



Proline is a nonessential amino acid which can be either obtained through a high protein diet or produced by the body from the amino acid Glutamate (Glutamic Acid).

What Roles Does Proline Play In The Body?

In addition to being used to build muscle proteins, Proline is also active in the brain where it functions similarly to Glutamic Acid but weaker.

It’s also required for Collagen synthesis, repairing injuries, and plays a role in fighting arteriosclerosis (hardening of the arteries).

Where Does It Come From?

Proline a non-essential amino acid so the body can produce it if you don’t get enough from your diet.  Proline is fairly easily produced by converting Glutamic Acid, but can also be found in high-protein foods.

  • Milk
  • Eggs
  • Meat
  • Fish
  • Cabbage
  • Seaweed
  • Asparagus

As with any non-essential amino acid, you want to aim for an adequate intake (which means getting enough complete proteins), but it’s not the end of the world if you’re a Vegan or Vegetarian and you’re diet lacks some Proline.

Your body can just make it.

Are There Any Benefits To Taking Proline Supplements?

Proline can be found in amino acid supplements, usually in the form L-Proline.  That said, it’s not particularly useful.

Key Takeaways For Proline

Proline is a nonessential, meaning your body can make it.  It’s also found in any complete protein food and various non-complete protein foods, so deficiency is extremely rare.

Although Proline is needed for the healthy functioning of our bodies, supplementation is unnecessary in most situations.



Serine is a non-essential amino acid which the body is able to manufacture from Glycine.

What Roles Does Serine Play In The Body?

Serine is required for a wide range of bodily functions including:

Those are just a few of the things Serine is involved in, but you get the idea.

While it doesn’t directly convert into any neurotransmitters or hormones, it’s very important.

Where Does It Come From?

As a non-essential amino acid, Serine can either be created by the body or obtained through a diet high in protein foods like:

  • Meat
  • Cheese
  • Eggs
  • Milk
  • Fish

If you’re a vegetarian or vegan, try eating Serine-rich plant-based foods like these:

  • Edamame
  • Seaweed
  • Soy
  • Watercress
  • Squash

Are There Any Benefits To Taking Serine Supplements?

Not really.  While Serine is certainly an important amino acid for maintaining all-around good health, Serine supplements don’t serve much of a purpose.  This is simply because Serine is easily obtained through your diet and made inside the body.

Deficiency would be the only reason to take a Serine supplement, but deficiency is rare.

Key Takeaways For Serine

Serine is a non-essential amino acid which supports a wide range of bodily functions and processes.  Supplementation is not particularly useful unless you’re deficient (unlikely).



Tryptophan is an essential amino acid which fulfills a vastly important role as precursor to Serotonin.

What Roles Does Tryptophan Play In The Body?

Not only does Tryptophan contribute to building muscle protein, it also happens to be the precursor to Serotonin, the “happy” neurotransmitter.

Serotonin is involved with regulating mood, sleep, appetite, and a whole lot more.  Since Tryptophan cannot be synthesized by the body, not getting enough through your diet can have a negative impact on neurotransmitter health.

Tryptophan deficiency can potentially result in depression, weight issues, and sleep disorders.  You definitely don’t want that!

Where Does It Come From?

Tryptophan is found in all complete-protein foods, including:

  • Meat
  • Dairy
  • Soy

It is allegedly the reason that Thanksgiving Turkey causes sleepiness.  In reality, Turkey contains roughly the same amount of Tryptophan as other meats.  You’re probably just tired because eating all that food caused the Insulin Spike of the year!

Are There Any Benefits To Taking Tryptophan Supplements?

The most common reason people take Tryptophan supplements is to improve sleep.  Research has shown mixed results though.  It’s definitely not as reliable as Melatonin for helping you get to sleep, remain asleep, or get better quality sleep.

Because Tryptophan converts to Serotonin, you won’t usually see it in amino acid supplements geared toward exercise.  Serotonin is believed to be a major contributor to exercise fatigue, so it just doesn’t make sense to include something that’s going to boost Serotonin during exercise.

Key Takeaways For Tryptophan

Tryptophan is an essential amino acid so you need to make sure your diet contains some.  The best foods for ensuring optimal Tryptophan are going to be high in protein.  If you don’t eat animal products, you need to make sure you get Tryptophan somehow.

Supplements can be used if you feel like your diet is lacking Tryptophan, though as a sleep supplement, it’s pretty over-hyped.



Tyrosine is a non-essential amino acid.  It can be either obtained through your diet or made by the body from the amino acid Phenylalanine.

What Roles Does Tyrosine Play In The Body?

Tyrosine is involved with muscle-building, as are all the proteinogenic amino acids, but that’s definitely not its most important role.

As the second step in Catecholamine synthesis (the step after Phenylalanine), Tyrosine is vital to various aspects of cognitive function including:

  • Mood
  • Stress Response
  • Energy/Focus
  • Memory/Learning
  • Sleep

Tyrosine and Phenylalanine are likely responsible for the cognitive benefits seen with a high protein diet.  Increasing the availability of these precursors supplies the brain with the supplies it needs to maintain healthy levels of Dopamine, Adrenaline, and Noradrenaline.

Where Does It Come From?

Tyrosine is found in high protein foods like:

  • Milk
  • Meat
  • Fish

But if you’re a vegetarian or a vegan, you may prefer to get your Tyrosine from foods such as:

  • Seaweed
  • Spinach
  • Mustard Greens
  • Beans

If you’re not getting enough Tyrosine, it’s not the end of the world because your body can just produce it using Phenylalanine as a starting point, but the benefits of a high-protein/high-Tyrosine diet are pretty obvious.

Tyrosine fuels a ton of cognitive activity.  Without it, cognitive decline is inevitable.

Are There Any Benefits To Taking Tyrosine Supplements?


When used as a supplement, you’ll usually find Tyrosine in the form of L-Tyrosine.  L-Tyrosine has been shown to help the body (and brain) adjust to stressful situations.  It does this by serving as the substrate for Catecholamine (Dopamine, Noradrenaline, and Adrenaline) synthesis.

L-Tyrosine doesn’t reduce stress.  It helps the body adapt to stress.

Key Takeaways For Tyrosine

Tyrosine is a very important amino acid, playing a vital role in Catecholamine synthesis.  You should ideally try to consume enough Tyrosine to fulfill it’s physiological roles, but if you don’t, your body can make it on its own.

You may find L-Tyrosine in amino acid supplements from time to time.  As a supplement, it’s been shown to help the body adjust to stress.



Valine is an essential amino acid and one of the 3 Branched Chain Amino Acids (BCAAs) along with Leucine and Isoleucine.

What Roles Does Valine Play In The Body?

As one of the BCAAs, Valine definitely plays a role in muscle-building, but it doesn’t directly stimulate muscle protein synthesis like Leucine.  In fact, Valine doesn’t seem to do much of anything on it’s own.

Aside from helping build proteins, Valine doesn’t have much on its plate.

Where Does It Come From?

Valine is an essential amino acid which means the body can’t manufacture it.  You must get it from the food you eat.

Foods that are high in Valine include:

  • Whey Protein
  • Meat
  • Fish
  • Seaweed
  • Watercress

Anything that contains BCAAs will also contain Valine, though the proportions tend to differ.

Are There Any Benefits To Taking Valine Supplements?

You’ll find Valine grouped in with BCAAs in amino acid supplements, but there’s no direct evidence that it really does much.  It’s just “one of the BCAAs” as far as most people are concerned.

Key Takeaways For Valine

Valine helps build muscle but not to a greater degree than any of the other essential amino acids.  It’s one of the 3 BCAAs, but doesn’t have unique benefits like the other 2.

As a supplement, Valine is pretty useless.  If you’re taking BCAAs, you’ll get some Valine.  As long as it isn’t used at the expense of Leucine and Isoleucine, there’s nothing wrong with this.

What About Non-Proteinogenic Amino Acids?

Remember, the term non-proteinogenic amino acids refers to any amino acid that is not used to construct whole proteins.  This is a pretty open-ended distinction, so naturally, there are quite a few of these.

However, we’ll just discuss a few of the more notable non-proteinogenic amino acids…


Taurine is technically not an amino acid.  It’s actually an amino sulfonic acid.  Since it’s made from two amino acids (Cysteine and Methionine) and widely distributed throughout the body (like an amino acid), we just refer to it as an amino acid.

Taurine is an antioxidant above all else, and this property is what underlies the majority of its physiological benefits.

Taurine can be found in foods like:

  • Meat
  • Eggs
  • Milk
  • Fish

But it does not naturally occur in most plants.  Only marine plants such as Seaweed contain Taurine.

This means that if you don’t eat animal products, you could be missing out on the awesome benefits of Taurine.

If this is the case, then supplementation may be a good idea.


L-Citrulline is the amino acid which serves as the precursor to Arginine.  Remember, Arginine is one of the most versatile amino acids.  It’s involved in a ton of processes and bodily functions.

Mostly notable:

  1. Nitric Oxide Production
  2. The Urea Cycle

Because it is the direct precursor to Arginine, Citrulline should be viewed as vital to these processes as well.

As a supplement, Citrulline has been shown to increase Nitric Oxide levels as well as enhance muscular endurance.  As it turns out, Citrulline supplements are actually better than Arginine supplements.  This is because Arginine supplements are subject to breakdown by the enzyme Arginase, while Citrulline supplements avoid that fate.


GABA may not be used to make proteins, but it is technically an amino acid in terms of its chemical structure.

In the brain, GABA serves as a the chief inhibitory neurotransmitter.  GABA receptors are the targets of drugs like Xanax and Valium which, when activated, calm the brain and slow mental activity.

In foods, GABA is created through the process of fermentation.  You won’t find it in the typical protein-rich foods we’ve been discussing.

Oddly enough, Cherry Tomatoes are one of the few commonly-eaten dietary sources of GABA.  Most plants don’t contain any though, leaving natural production (from Gluatmic Acid) and supplementation the only options.


Ornithine is an intermediate in the Urea Cycle.  This is the process by which Ammonia (which is toxic) is converted into Urea (which is non-toxic) which is then excreted from the body (in the form of Urine).

As a non-proteinogenic amino acid the presence of Ornithine isn’t guaranteed in complete-protein foods, but coincidentally, it can still be found in many of them:

  • Meat
  • Dairy
  • Fish
  • Eggs

Ornithine supplements are also an alternative way to make sure you’re getting enough.

There is evidence which suggests supplementing with Ornithine prior to working out can help with muscular endurance and fatigue.  It’s similar to Citrulline in this regard, but Citrulline has a lot more research behind it.


Beta-Alanine, as the name implies, is the beta-version of the amino acid Alanine.

It is used by the body to create Carnosine, an antioxidant dipeptide, higher levels of which have a proven correlation with better muscular endurance.

Carnosine acts as a Lactic Acid buffer in muscle tissue.  This delays muscular fatigue (which is caused in part by Lactic Acid build-up).

Since Beta-Alanine (not Histidine) is the rate limiting factor, that’s all you need to boost muscle Carnosine levels.

Foods that contain Beta-Alanine include:

  • Meat
  • Fish
  • Soy

Taking a Beta-Alanine supplement is also a great way to ensure adequate Beta-Alanine is available for Carnosine synthesis.


Carnitine isn’t exactly an amino acid.  It’s technically a dipeptide (2 amino acids combined) made from Methionine and Lysine.  However, since it’s often used in amino acid supplements, many people just refer to it as an amino acid.

It’s required for a number of phsyiological functions, one of the most important being Fatty Acid transport into the Mitochondria of the cell.

Without Carnitine, a critical step in the fat-burning process would be compromised.  That’s why Carnitine deficiency is characterized by hindered fat-burning capabilities.

Carnitine also plays an important role as an antioxidant, helping to reduce oxidative damage in various tissues through the body.

Foods which contain Carnitine include:

  • Meat
  • Dairy
  • Seafood
  • Asparagus
  • Whole Wheat Bread

The only individuals who are likely to be Carnitine deficient are those who don’t eat any animal products.  If that’s you, you should consider taking a Carnitine supplement.

5 Amino Acid Supplements That Are Actually Worth Taking (And Why)

Although there are a number of amino acid supplements out there, the majority of them are worthless.  The truth is most amino acids don’t need to be consumed in the form of supplements.  Unless you eat a low-protein diet, you’re probably already getting the necessary amounts of most of the important amino acids.

However, there are some exceptions.  Some amino acid supplements are actually worth taking.

Citrulline – proven to increase Nitric Oxide levels and enhance muscular endurance.

Taurine – proven to reduce oxidative damage during exercise.

Beta-Alanine – proven to increase muscle Carnosine concentrations and enhance muscular endurance.

Leucine – proven to directly stimulate muscle protein synthesis.  Useful for low-protein diets and fasted training.

Carnitine – proven to reduce oxidative damage in muscle tissue.  May enhance exercise performance.


What About Essential Amino Acid (EAA) Supplements?

Essential Amino Acids (the ones the body can’t make) have become a sub-category of their own within the amino acid supplement category.  The idea goes something like this..

Because you can’t make EAAs yourself, taking an EAA supplement ensures that you’re getting adequate levels of these amino acids and can enhance muscle protein synthesis.

Indeed, preliminary research has revealed that EAA supplementation may be useful for elevating post-workout muscle protein synthesis rates, but there is absolutely no evidence that it’s better than a protein supplement or an actual meal.

In fact, logic would suggest that the protein shake or the meal would be ideal, since they would both provide a complete array of macronutrients, not just a few amino acids.

So it’s not really a question of whether EAAs help.  Sure they do, but the question is really “are they worth paying a premium”.  To that, the answer is no.  You’re better off just sticking with a post-workout protein shake to hold you over until you can eat a real meal.

Just because they’re considered essential doesn’t mean you have to pay extra for them.

The Bottom Line On Amino Acid Supplements

The harsh reality about amino acid supplements is…Most of them are garbage!  If you’re getting enough protein, you don’t stand to benefit from most amino acids, but there are some that are actually worth supplementing with.

Have anything to add about amino acids or amino acid supplements?  Comment below!

I’m Matt Theis, founder of SuppWithThat, Momentum Nutrition, and Singular Sport. I created SWT to separate the science from the hype and publish accurate, research-based information on supplements. If you like what I have to say here, feel free to check out my supplements at and

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